Ceiling grid system expansion joint

ABSTRACT

A structural main beam for use in the supporting lattice or grid of a fire rated suspended ceiling comprising a longitudinally extending web having bulb and flange portions located along opposite upper and lower marginal edges thereof, and including coupling means at opposite longitudinal ends for expandably interlocking a pair of beams in end to end relationship. Thermal expansion of the beam is localized in the interlocking coupling means and in at least one deformable section formed by a pair of vertically oriented apertures or cut outs in the web, the apertures being disposed proximate each of the bulb and flange portions respectively to permit bending thereof whereby the integrity of the ceiling is substantially maintained when subjected to extremely high thermal stresses such as can occur during exposure to a fire.

Nov. 5, 1974 Adams 3.496.690 2/l970 Jahn....

[ CEILING GRID SYSTEM EXPANSION 33 r. o b r A n n A S m a d We rh mm GMm JII- H 7 .l.

S .N .w A m w L D: NP. A R MO 5 6 m E n 3 WP HN MG 5 R O F 848,ll5 81970 C- zd' 52 BK. 5 [73] Assignee: Rollform Incorporated, Ann Arbor, II J Primary Examiner-Thomas F. Callaghan Agent, or Firml-iarness, Dickey& Pierce Mich.

Apr. 4, 1972 [22] Filed:

Attorney,

ABSTRACT [21] Appl. No.; 240,921

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n o wfmm m m T08 61 h h Tw mam 5mm [56] References Cited UNITED STATESPATENTS g disposed proximate each of the bulb and flange ortionsrespectively to permit bending thereof by the integrity of the ceilingis substantially maintained when subjected to extremely high thermalstresses such as can occur during exposure to a fire.

12 Claims, 3 Drawing Figures S e r u t fl 6 P a e h t b e w e h t .m S tu o t U C r o S e r u t r e P a d ebP where 33 A A 6556 3 9559 8 .8 l..l u/

. 7 7 n 00 00 u 2 2 m mmmmml u. n u U n uunnuunt mn n ye m m m U I nwe$tmo m mo [6 n r. i km .1 mmflnflwnm onkflaofln CZL-JHDJZ 456600008966666666 99999999 .llllllll. 26 26007 1 ll CEILING GRID SYSTEM EXPANSIONJOINT BACKGROUND AND SUMMARY OF THE INVENTION This invention relatesgenerally to fire rated ceilings, and more particularly to an improvedstructural main beam for use in the associated supporting lattice orgrid structure therefore.

As is well known, when accoustical ceilings are suspended from aconventional ceiling or overhead structure, the air space definedtherebetween provides insulation for resisting heat transfer and in theevent of a fire is most valuable for limiting the fire to the spacebeneath the suspended ceiling. It is also well known however that whenthe grid or lattice system supportingthe suspended ceiling is subjectedto substantial thermal stresses, the structural beams including both thelongitudinal main beam and the cross beams'which form the supportinglattice, tend to twist and buckle. This occurrence has been found tolift and sometimes dislodge the heretofore supported ceiling panelsthereby exposing the superstructure to the fire and thus allowing thefire to spread more rapidly than would otherwise be the case. In a firerated ceiling, various means have been proposed to localize the thermalexpansionof the lattice whereby the integrity of the suspended ceilingissubstantially retained or at least retained for anincreased timeinterval. The subject invention is addressed to a main structural beamfor use in a fire rated suspended ceiling assembly which is adapted tofunctionally retain the integrity of such a ceiling. It is therefore theprimary object of the subject invention to provide an improvedstructural main beam for a suspended ceiling assembly which is adaptedto localize and control thermal expansion and thereby substantiallymaintain the integrity of the suspended ceiling during exposure to afire. I

In the subject invention the thermally responsive structural beamincludes a web portion having a continuous flange on one spaced marginaledge and a bulb or rolled over portion along an opposite marginal edge.A pair of vertically spaced rectangular apertures or cut outs arelocated adjacent the bulb and flange portions, respectively, and areadapted to provide localized deformation of the flange and bulb portionin response to longitudinal expansion of the beam. For purposes ofsupporting the ceiling panels and other ancillary associated structure,it is desirable that the deformable section be devised in such a manneras to obviate the need for additional bracing or reinforcing members forsupporting the ceiling load. In beams requiring additional reinforcingmembers, the design of the beam itself becomes more complex andcorrespondingly more costly to produce. It is therefore a general objectof the subject invention to provide a beam having a localized deformablesection not requiring additional reinforcement to support normal ceilingloads thereby simplifying the design and fabrication thereof.

In another aspect of the invention the main structural beams are adaptedto be connected in end to end relationship by means of an expandibleinterlocking coupling arrangement devised to provide expansion relief inresponse to exposure of induced stresses. It is therefore another objectof the subject invention to provide an expandible interlocking couplingarrangement for longitudinally joining a pair of main beams in end toend relationship.

It is another object of the subject invention to provide an improvedmain beam for an accoustical ceiling construction that provides apositive fire barrier between the floor and the ceiling of an enclosedspace.

It is still another object of the subject invention to provide anaccoustical ceiling construction that accomplishes longitudinalexpansion of the grid members of an accoustical ceiling grid system.

It is a further object of the subject invention to provide a main beamfor a lattice structure adapted for supporting accoustical panels thatmaintain structural integrity over relatively high ambient temperatureconditions.

It is still a further object of the subject invention to provide astructural main beam of the above character BRIEF DESCRIPTION OF THEDRAWINGS FIG. 1 is an enlarged fragmentary prospective view of a pair ofmain structural beams in accordance with the subject invention adaptedfor forming a part of a supporting lattice of a suspended ceiling andillustrated with a pair of fragmentary cross beams before assemblythereof;

FIG. 2 is an enlarged fragmentary prospective view of the end portionsof the pair of main structural beams illustrated in FIG. 1 illustratingthe pair of beams interlockingly connected;

FIG. .3 is an enlarged fragmentary prospective view of the structureillustrated in FIG. 1 with the cross beams assembled thereto and afterthe assembly has been exposed to a substantial thermal load; and

FIG. 4 is an enlarged, fragmentary plan view looking in the direction ofthe arrows 4-4 in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In a fire ratedsuspended ceiling, a plurality of main structural beams are generallylocated in spaced parallel relationship, with the spacing generallycorresponding to an edge dimension of a ceiling panel such as anacoustic tile, a gypsum board, or the like and adapted to be supportedby laterally extending flanges located on the lower end of each of thebeam members forming the lattice. The space between adjacent mainstructural beams is likewise subdivided by means of suitable cross beamsappropriately located on centers which accommodate the adjacent edgedimensions of the ceiling panels to be suspended. The cross beams areadapted to be supported at their extremities by the main beams and areusually located in perpendicular relationship thereto. As shallhereinafter be described, and in accordance with the subject invention,the cross beams are flexibly interlocked. in suitable slots located inthe web of the main beams and adapted for maintaining the integrity ofthe system during a fire.

With reference now to FIG. 1 of the drawings a structural main beam isindicated generally at 10, the beam l0'being adapted for use in forminga supporting lattice for a fire rated suspended ceiling. The beam 10 iscommonly referred to in the trade as a T-member because of its generallyinverted T-shaped vertical cross crosssection and, as shown, the beam orT member is comprised of a vertically extending web 12, a ceiling panelsupporting flange 16 which extends laterally from opposite sides of theweb 12 and an enlarged bulb 14 of generally rectangular shapedcross-section. As illustrated, the member 10 is shown in abutting end toend relationship with an identical structural beam 10', the beam 10'having a web 12', a bulb 14' and a laterally extending flange 16'. Forpurposes of clarity, the beam 10' is designated by like numerals used todesignate the beam 10 but with the addition of a prime suffix. In thesubject invention the structural beams 10 and 10' are slidably heldtogether and guided by an interlocking arrangement which permits the useof standard length beam members, e.g., 12 feet, in various multiples orparts thereof to accommodate different spans.

To form a supporting lattice for a suspended ceiling, the structuralbeam members 10 and 10' are installed in parallel rows spaced apart adistance substantially equal to or slightly greater than an edgedimension of a ceiling tile (not shown) to be used whereby paralleledges of the panels are supported in flanges, such as the flanges l6 and16', respectively. The beams 10 and 10' include a plurality of spacedapertures 18 adapted to receive suitable hangers (not shown) forsupporting the grid system from the superstructure, and spaced sets ofvertically oriented slots 20, the latter being used for receiving tabs22, for interconnecting suitable cross beams 24 and 24, respectively tothe member 10. The cross beams 24 and 24' also are generally inverted T-shaped in cross-section and each include web, bulb, and flange portionssubstantially identical to the web 12, bulb l4, and lateral flange 16 ofthe beam 10. Additional sets of apertures are longitudinally spaced inthe web 12 of the beam 10 and are adapted to receive projecting tabs ofother cross beams (not shown). The sets of apertures are preferablylongitudinally spaced I flanges of the cross beams so that the gridssystem formed by the main structural beams and the cross beams define asubstantially rectangular lattice. The

rectangular lattice together with ceiling panels supported thereonpresent an aesthetically pleasing and accoustically superior ceiling forthe enclosure. The details of the interlocking relationship between themain structural beams 10 and 10 and the cross beams 24 and 24' form nopart of the present invention and are included herein for clarity.Reference may be had, however, to US. Pat. No. 3,396,997 for a detailedexplanation as well as an illustration and explanation of the gridsystem formed thereby, the patent being assigned to the assignee of thesubject invention and the grid system due to thermal expansion, thecross beams 24 and 24' can be permitted to expand in a manner describedin US. Pat. No. 3,396,997 previously incorporated herein by reference.Correspondingly. the main beams 10 and 10 also expand under theinfluence of thermal expansion and due to the substantially greaterlength thereof, the expansion must be controlled to retain the integrityof the lattice.

In the subject invention, the coupling means for interlocking the mainstructural beams 10 and 10' in end to end relationship are adapted toprovide expansion relief. As best observed in FIG. 1, the end of thebeam 10 includes a projecting web portion 28 spaced slightly outwardfrom the plane of the web 12 and defining a vertical shoulder 27therewith, and a generally rectan-' gularly shaped tab 30 which deflectsslightly inward relative to the web 12' of the beam 10'. Moreover, a tabengaging aperture 34 is suitably located to the left of the end portion28 and adapted for receiving a tab 30' as defined in the abutting end ofthe beam 10'. For ease in assembly and for obviating the need foradditional reinforcement, when interlocking the beams 10 and 10', thetab 30 is convergentially tapered outwardly, the inner verticaldimension being substantially equal to the vertical dimension of theaperture 34. Thus it will be seen that the inner portion of the tabprovides a retainer slide or guide for the beam assembly when engaged inthe tab engaging aperture. The bulb sections, however, 14 and 14' ofeach of the beams 10 and 10', respectively, is suitably undercut anddefines vertically extending shoulder portions 32 and 32', respectively,which normally provides a longitudinally extending void in the bulbportions when the beams are interconnected in end to end relationship.The beams 10 and 10' are interconnected by locating the tabs 30 and 30in the tab receiving apertures 34 and 34', respectively, and thensuitably reversely folding over the tabs therethrough. As shallhereinafter be explained, the longitudinal distance between theshoulders 32 and 32', re spectively define the limits of a slidableexpansion relief point, the operation of which will be hereinafterdescribed in conjunction with the operation of the beam 10 whensubjected to a fire.

ln'addition to the expansion provided by the interlocking couplingmeans, the main structural beams 10 and 10 include, at least, onelocalized expansion joint whereby thermal expansion can be localized toa selective area or zone of the beam, and the integrity of the systemcan be maintained. To this end the web 12 of the beam 10 is seen toinclude a generally rectangular shaped cutout area or slot 36 whichdefines a continuous marginal strip 46 of substantially uniform widthbetween the lower edge of the aperture and the flange 16. A V-shapednotch 38 formed in the strip substantially at the substantial at themidpoint of the lower edge of the aperture 36 extends downwardly towardthe flange 16. A second elongated rectangular slot or cut out 40 ofslightly longer longitudinal dimension and centrally disposed and spacedabove the cut out 36 defines a continuous marginal strip 48 alsopreferably of substantially uniform width adjacent to the bulb 14.Preferably the bulb 14 includes suitable vertical suppression points orcreases 44 oriented in accordance with the midpoint and end edges of theslot 40 to provide stress concentration points in the bulb 14 as showngenerally in FIGS. 1 and 3 and in greatly exaggerated form in FIG. 4.The rectangular cut outs 36 and 40 are adapted to permit lateral bendingof the bulb 14 and of a section 42 of the web 12 disposed between theslots 36 and 40 and downward bending of the flange 16 in response tothermal expansion of the beam 10.

In operation, when the beam is exposed to a fire, the flange 16 issubjected to the highest thermal loading due to its location in directconfrontation therewith. The bulb portion 14 located on the oppositevertical end of the beam however is exposed to a substantially lessthermal loading due to its vertical position above the flange andgenerally speaking is only indirectly subjected to the high temperaturesource. With reference now to FIG. 3, the beam 10 is illustrated in itsexpansion relief state. More particularly it will be seen that theflange l6 buckles downwardly due to the eminence of the V-notch 38disposed midway in the slot 36 providing stress concentration in the web12 and more particularly described in the patent to Adams, US. Pat. No.3,350,125, the patent also being incorporated herein by reference. Theportion 42 on the other hand being located between the slots 40 and 36deforms laterally while the bulb portion 14 is deflected laterally butto a lesser extent due to less thermal loading. it will be noted,however, that the buckling is localized and that the beam will stillretain the supported ceiling panels.

With reference to the right end of the beam 16 and as again illustratedwith reference to FIG. 3, it will be seen that the flange l6 deflectsupwardly in response to thermal expansion of the web 12 of the beam 10to drive the shoulders 32 and 32' into abutting confrontation.Simultaneously the folded over tabs and 30 longitudinally and guidablyslide along the outer surfaces of web 12 and 12' and provide a slipjoint therebetween. Thus jamming relief at the juncture between thebeams 10 and 10 is adequately provided to at least partially relieve thethermal expansion of the beams 10 and 10' while maintaining theinterconnection thereof.

In a preferred form of the beam 10, two expansion relief cut outs, eachcomprised of the slots 36 and 40 are located inwardly a selectivedistance from each opposite longitudinal end of the beam 10. By havingtwo expansion relief cut outs, the elongation is more evenly distributedin the beam and the structural characteristics and integrity isenhanced. Thus, the subject beam provides an improved grid system for asuspended ceilmg.

While it will be apparent that the preferred embodiment of the subjectinvention disclosed herein is well calculated to fulfill the objectsabove stated, it will be appreciated that the invention is susceptibleto modification, variation, and charge without departing from the properscope or fair meaning of the subjoined claims.

What is claimed is:

l. A controlled expansion beam for use in a ceiling grid systemcomprising:

a longitudinally elongatedweb having a lower flange adapted to supportthe marginal edge portion of a ceiling panel and an upper continuousbulb portion; and

means formed in said web intermediate the ends of said beam providing acontrolled localized expansion relief section for said beam, said meansincluding upper and lower longitudinally elongated apertures formedsolely in said web one above the other and disposed in spacedrelationship between said flange and said bulb portion, said aperturesdefining longitudinally extending upper and lower continuous marginalstrips in the web along and adja- 5 cent to said bulb portion and saidflange, said marginal strip located adjacent to said flange being ofsubstantially uniform width and provided intermediate the ends thereofwith only a single mediunly disposed notch means which extendsdownwardly from said lower aperture and terminates short of said flangefor controlled downward buckling of said flange in response tolongitudinal compressive forces applied to said beam.

2. The beam as recited in claim 1 wherein said bulb includes a pluralityof creases proximate said upper aperture to facilitate lateraldeflection of said bulb when said beam is compressed longitudinally.

3. The beam as recited in claim 1 wherein said upper and lower aperturesfurther define a relatively thin strip 20 in said web between saidapertures and said upper and lower marginal strips which is adapted todeflect laterally under longitudinal compression of said beam.

4. The beam as recited in claim 1 wherein a controlled localizedexpansion section is provided adjacent each end of said beam.

5. The beam as recited in claim 1 wherein the upper of said apertures islonger than said lower aperture.

6. The beam as recited in claim 1 including means located proximate, atleast, one end of said beam for interlockingly connecting said beam inend to end relationship with a beam of similar configuration.

7. The beam as recited in claim 6 wherein said means includes atabprojecting outwardly from said web, and an aperture located inwardlyin said web relative to said tab.

8. The beam as set forth in claim 1 wherein said bulb portion is cutback at an end of said beam and including means at said end of said beamfor connecting the lat- 40 ter in endwise butting relation to anothersimilar beam, said means adapted to permit the interconnected ends ofsaid beams to slide toward each other within limits defined at least inpart by the cut-back of said bulb portion. 9. The beam as set forth inclaim 8 wherein said means comprises a generally rectangular apertureadjacent to the mentioned end of said beam, and a longitudinal tongue onsaid end laterally offset from the plane of the web of said beam, saidtongue adapted to extend alongside the web of said other similar beamand to be folded back through a similar aperture in said other beam,said tongue adapted further to slide longitudinally in said aperture andfitting snugly between the upper and lower edges thereof normally andduring sliding movement thereof to hold said beam and said other beamsubstantially in alignment with each other. 10. A controlled expansionbeam as recited in claim 1 further including a second beam substantiallysimilar to the first recited beam and disposed in endwise buttingrelation with said first recited beam; and means providing a slidinginterlocking connection between said beams, said means holding thebutted ends of said beams rigidly together and in alignment with eachother while permitting said ends to 7 8 crush together when said beamsare compressed ening the beams so that they are likely to bedamlongitudinally as under thermal expansion, the bulb aged by normalhandling. portions of both beams being cut back and spaced 12. A pair ofcontrolled expansion beams as set forth apart at the butted ends of thebeams to facilitate in claim 10 wherein said means comprises crushingtogether of said beams and the cutback a generally rectangular apertureadjacent to the ends of said bulb portions adapted to interengage buttedend of each beam, and to limit the extent to which said beams can crusha longitudinal tongue on the butted end of each beam together to relievecompressive forces in said extending alongside the other of said beamsand beams. being folded back through the aperture in said 11. A pair ofcontrolled expansion beams as set forth 1 other beam, in claim whereineach of said beams is provided adsaid tongues being longitudinallyslidable in said apjacent each end thereof with an expansion reliefsection ertures when the butted ends of said beams crush of the typespecified in claim 1, together and snugly fitting between the upper andsaid expansion relief sections and the cut-backs in the lower edges ofsaid apertures to hold said ends in bulb portions of said beams beingmutually collecalignment with each other normally and at least tivelyoperable to absorb and relieve forces of longenerally while said beamsare crushing together. gitudinal compression in said beams without weak-

1. A controlled expansion beam for use in a ceiling grid systemcomprising: a longitudinally elongated web having a lower flange adaptedto support the marginal edge portion of a ceiling panel and an uppercontinuous bulb portion; and means formed in said web intermediate theends of said beam providing a controlled localized expansion reliefsection for said beam, said means including upper and lowerlongitudinally elongated apertures formed solely in said web one abovethe other and disposed in spaced relationship between said flange andsaid bulb portion, said apertures defining longitudinally extendingupper and lower continuous marginal strips in the web along and adjacentto said bulb portion and said flange, said marginal strip locatedadjacent to said flange being of substantially uniform width andprovided intermediate the ends thereof with only a single medianlydisposed notch means which extends downwardly from said lower apertureand terminates short of said flange for controlled downward buckling ofsaid flange in response to longitudinal compressive forces applied tosaid beam.
 2. The beam as recited in claim 1 wherein said bulb includesa plurality of creases proximate said upper aperture to facilitatelateral deflection of said bulb when said beam is compressedlongitudinally.
 3. The beam as recited in claim 1 wherein said upper andlower apertures further define a relatively thin strip in said webbetween said apertures and said upper and lower marginal strips which isadapted to deflect laterally under longiTudinal compression of saidbeam.
 4. The beam as recited in claim 1 wherein a controlled localizedexpansion section is provided adjacent each end of said beam.
 5. Thebeam as recited in claim 1 wherein the upper of said apertures is longerthan said lower aperture.
 6. The beam as recited in claim 1 includingmeans located proximate, at least, one end of said beam forinterlockingly connecting said beam in end to end relationship with abeam of similar configuration.
 7. The beam as recited in claim 6 whereinsaid means includes a tab projecting outwardly from said web, and anaperture located inwardly in said web relative to said tab.
 8. The beamas set forth in claim 1 wherein said bulb portion is cut back at an endof said beam and including means at said end of said beam for connectingthe latter in endwise butting relation to another similar beam, saidmeans adapted to permit the interconnected ends of said beams to slidetoward each other within limits defined at least in part by the cut-backof said bulb portion.
 9. The beam as set forth in claim 8 wherein saidmeans comprises a generally rectangular aperture adjacent to thementioned end of said beam, and a longitudinal tongue on said endlaterally offset from the plane of the web of said beam, said tongueadapted to extend alongside the web of said other similar beam and to befolded back through a similar aperture in said other beam, said tongueadapted further to slide longitudinally in said aperture and fittingsnugly between the upper and lower edges thereof normally and duringsliding movement thereof to hold said beam and said other beamsubstantially in alignment with each other.
 10. A controlled expansionbeam as recited in claim 1 further including a second beam substantiallysimilar to the first recited beam and disposed in endwise buttingrelation with said first recited beam; and means providing a slidinginterlocking connection between said beams, said means holding thebutted ends of said beams rigidly together and in alignment with eachother while permitting said ends to crush together when said beams arecompressed longitudinally as under thermal expansion, the bulb portionsof both beams being cut back and spaced apart at the butted ends of thebeams to facilitate crushing together of said beams and the cutback endsof said bulb portions adapted to interengage to limit the extent towhich said beams can crush together to relieve compressive forces insaid beams.
 11. A pair of controlled expansion beams as set forth inclaim 10 wherein each of said beams is provided adjacent each endthereof with an expansion relief section of the type specified in claim1, said expansion relief sections and the cut-backs in the bulb portionsof said beams being mutually collectively operable to absorb and relieveforces of longitudinal compression in said beams without weakening thebeams so that they are likely to be damaged by normal handling.
 12. Apair of controlled expansion beams as set forth in claim 10 wherein saidmeans comprises a generally rectangular aperture adjacent to the buttedend of each beam, and a longitudinal tongue on the butted end of eachbeam extending alongside the other of said beams and being folded backthrough the aperture in said other beam, said tongues beinglongitudinally slidable in said apertures when the butted ends of saidbeams crush together and snugly fitting between the upper and loweredges of said apertures to hold said ends in alignment with each othernormally and at least generally while said beams are crushing together.